Methods of controlling the process of agglomeration

ABSTRACT

A method of agglomerating mineral materials by mixing them with fuel and then water and sintering, including the steps of continuously monitoring the process of agglomeration by measuring the permeability of the mixture before sintering and regulating the supply of water to ensure an appropriate permeability of the mixture to be sintered for the highest speed of sintering and for the desired quality of the agglomerate, said regulation of water supply process as a whole and of foreseeable disturbances in the process.

41) United States Patent 1 1 3,615,366

[72] Inventors Henry Gilbert Meunier; [56] References Cited! Johannes Joseph Lockers, both of Liege, UNITED STATES PATENTS [21] A 1 No ggzfg l 2,888,026 5/1959 Henderson 6161 324/41 21 [22] f 29 1968 2,980,291 4/1961 Schuerger 75/5 11x [45] Patented oct'ulml 3,138,014 6/1964 .lorre 75/5 X 3,148,971 9/1964 MacDonald et a1. .1 75/5 [73] Ass1gnee Centre National ole Reclrerches 3 153 587 10/1964 Schuerger giffg g g j 3,194,546 7/1965 Schuerger et a1. 75/5 x 3,211,441 10/1965 Miyakawa et a1 75/5 X pmmes gzf' i l 3,249,422 5/1966 Sironi et a1 75/5 [31] 7073459 3,265,377 8/1966 Cappel 75/5 x 9 1319, Belgium 110-7117133707 iili'i3 251323 313312;: 324/11 Primary Examiner-Allen B. Curtis Attorney-Holman & Stern ABSTRACT: A method of agglomerating mineral materials by mixing them with fuel and then water and sintering, including [54] g ggi gfii gfigg THE PROCESS or the steps of continuously monitoring the process of ag- 6 Cl 2 D glomeration by measuring the penneability of the mixture berawmg fore sintering and regulating the supply of water to ensure an [52] U.S. Cl 75/5 appropriate permeability of the mixture to be sintered for the [51] lint. Cl C211) 1/10 highest speed of sintering and for the: desired quality of the ag- [50] Field of Search..... 75/1-5; glomerate, said regulation of water supply process as a whole and of foreseeable disturbances in the process.

PATENTEDCBI 2619?! 3,615,344

SHEET 2 OF 2 HENRY GIL 49) METHODS OF CONTROLLING THE PROCESS OF AGGLOMERATION The present invention relates to a method of controlling the process of agglomeration, which method is of particular relevance to the case of the agglomeration of mineral materials and in particular ferrous minerals.

In talking of ferrous minerals, it is intended to indicate here either a mineral of single origin which is either rich or poor in iron, or a mixture of two or more minerals which are rich and/or poor in iron. This definition applies, mutatis mutandis, in respect of any other mineral substance whose state and properties allow it to be agglomerated.

It is also important at this point to explain that in the present text and in the claims, the expression materials to be agglomerated" will be used not only in the sense of a mixture of mineral materials such as a ferrous mineral or minerals, with a fuel such as coke and with return fines, but also to indicate each of these various materials considered separately or in mixtures of two.

Finally, it should be emphasized that the expression agglomerated materials" also used in the present text and in the claims, includes materials which are composed as to one part of agglomerates proper, i.e. they are agglomerated to a sufficient extent for their ultimate use, and as to the other part of return fines.

The purpose of the regulation and optimizing of the agglomeration process, is to produce agglomerated materials of constant quality under optimum conditions.

The desired quality in the agglomerated materials, that is to say their cohesion and their reducibility, is generally defined by the consumers and in particular by blast furnace specialists. Obviously, one has to allow for an inevitable degree of compromise between these properties, but generally speaking consistency in the properties of the agglomerated materials is required to ensure, in the case of the blast furnace for example, unifonn operation.

As far as defining optimum conditions of manufacture is concerned, various essential factors have to be taken into account. In particular, the consideration of operation at maximum production capacity and that of attaining the lowest possible selling price, are not necessarily compatible.

The result is that there is a variety of concepts to take into account as far as the factors to be controlled and regulated in the process are concerned, and also regards the means to be employed.

The various aspects of the problem are as follows:

1. The stabilization of the composition of the mixture of materials to be agglomerated;

2. Stabilization of the point of breakthrough in the flame front;

3. The control of the permeability of the crude mixture;

4. The control of the quality of the agglomerated materials.

The present discussion is directed exclusively to points 3 and 4 of the above.

Controlling the Permeability of the Mixture of Materials to be Agglomerated.

The permeability of the mixture of materials to be agglomerated is the most important factor where the determination of the speed of agglomeration is concerned, since one particular value of this factor corresponds with a maximum rate of agglomeration.

In addition, it is well known that the permeability of a mixture of materials to be agglomerated, is itself principally and strongly influenced by the moisture content of said mixture. In order to adjust the permeability to the desired value, the simplest and most efficient mode of operation consists in influencing the overall moisture content of said mixture by modifying the quantity of water added to it before it un dergoes the agglomeration process. In other words, the total moisture content of the mixture is equal to the moisture content produced by the water added to the mixture, plus the initial moisture content of the mixture, that is to say its moisture content prior to the addition of any water.

It should be born in mind that the relationship between the total moisture content of the mixture and the permeability thereof, is a nonlinear function.

Experience has shown that stabilization of the permeability automatically leads to a stabilization of the total moisture content of the mixture.

Nevertheless, it must be born in mind that the relationship between the permeability and the total moisture content of the mixture, modifies over the course of time, as a consequence of fluctuations in the characteristics of the mixture and in particular its granulometry. Modifications of this kind make it necessary as a consequence to modify the permeability in order to maintain it at an instantaneous optimum level: this kind of adaptation therefore constitutes an optimizing of the process of agglomeration.

In order to achieve optimum operation of the agglomerate production line, it is not sufiicient to keep the total moisture content of the mixture constant. nor simply to keep the permeability constant, but it is also necessary for the permeability to be adjusted to an optimum value at every instant.

It is also necessary to take into account the dynamics of the process when modifying the quantity of water added to the mixture in order to adjust its permeability. The problem here is that of foreseeable disturbances which have to be taken into account, and in particular their rate of variation. Considering the stability of the permeability function, the techniques of control have made it possible to tabulate the delay time elapsing between the instant at which water is added and the instant at which the corresponding change in the permeability takes place.

As far as unforeseeable disturbances are concerned, all that one can do is to detect them at the output of the process, although it is not possible to say what is their cause nor to say in precisely what way they have influenced the process.

The principle of permeability measurement is well known:

It consists in supplying air at constant pressure through the mixture using a nozzle which penetrates into it to a certain depth, and in measuring the airflow rate. The present applicants have carried out a special study with the purpose of achieving adequate sensitivity of measurement in this direction. The device by which this measurement is carried out is called a permeameter" in the present description and has been disclosed in Belgian Pat. Nos. 628,598; 673,409; 674,864; 682,293 and Luxembourg Pat. Nos. 47,508; 47,716;

48,188; 48,225; 48,274; 55,664, and one other, as yet not numbered, dated 10.10.1968.

Controlling the Quality of the Agglomerated Materials.

Of all the properties of agglomerated materials, the cohesion which is responsible for their mechanical strength, is a factor of prime importance where the consumer is concerned, in particular where blast furnace operators are concerned.

Numerous studies have shown that the molecular composition of agglomerated materials has a correlation with the properties and in particular with the cohesion and reducibility, of said agglomerated materials.

Molecular analysis by X-ray diffraction techniques, at present makes it possible to determine directly with a high degree of accuracy, the contents of haematite, magnetite and wustite, in the agglomerated materials. By taking the difference between the total iron and the iron determined by X- ray diffraction, it is possible to determine the combined iron, in particular the iron combined in the form of ferrites of aluminosilicates of lime. The importance of these determinations resides in the following two considerations:

a. In respect of agglomerates manufactured from one and the same mixture, there is a clear relationship between the results of analysis and the properties of the sintered product. Certain variations can be allowed in the composition of the crude mixture, without effecting this relationship;

b. The structure of the agglomerates during the course of manufacture, does not change in other than a progressive manner and therefore has a certain degree of uniformity in time.

The practical result of this control is to facilitate the determination of the minimum fuel content in order to achieve the desired cohesion between the agglomerates.

Thus, when the haematite content exceeds a certain level, this may be the sign that the fuel input is too low and that the mechanical strength of the agglomerate is falling off. On the other hand, the formation of wustite is always the sign of an excess of fuel.

The two other components, that is to say the magnetite and the lime ferrites, explain the cohesion of the agglomerated materials.

However, the magnetic materials, are related to their content of magnetite and lime ferrites.

This means that the measuring of the magnetic properties of agglomerated materials can be employed to determine their quality and in particular their cohesion.

A simple method adopted by the present applicants, in order to measure the magnetic properties of agglomerated materials, consists in taking a representative sample of the said materials and passing it through the magnetic circuit of a solenoid, said materials thus acting as part of the core of the solenoid. The result is that the characteristics of the magnetic circuit of the solenoid depend upon the state and properties of said agglomerated materials, that is to say upon their quality. Consequently, the continuous measurement .by a known means, of the characteristics of the said solenoid, can be used to provide an indication of the quality of the said agglomerated materials.

The device likewise used by the present applicants and enabling the measurement of the magnetic properties of the agglomerated materials to be carried out, is referred to in the present description by the term permagnag and has been made the subject of Luxembourg Pats. 50,769; 53,954; 54,035; 54,010 and Belgian Pats. 707,292; 707,458 and 41,937 (application number).

it is the object of the present invention to provide a method for the continuous control of the agglomeration process, by means of which the operational conditions can be maintained at an optimum, or returned to said optimum state in the event of any disturbance. The method is based upon measurements of the permeability of the materials to be agglomerated and/or of the magnetic properties of the agglomerated materials, in the manner defined hereinbefore.

The invention will now be described making reference to the accompanying drawings which illustrates the invention but in no restrictive sense.

FIG. 1 illustrates schematically in a nonlimitative way a general installation for the line production (conveyor system) of ferrous mineral agglomerates.

The supply circuit for the agglomerating installation comprises three hoppers 1 containing the mineral, another hopper 2 containing the returned fines and a third 3 containing fuel, such as coke. These hoppers are designed to charge appropriate quantities of the mineral, the fines and the fuel, onto a conveyor 4 going to a mill or mixer 5 where the mixture which is to be agglomerated, is formed. When the materials have been introduced into the mill or mixer 5, there is added to them a carefully determined quantity of water, through the I valve 6.

At the output from the mill 5, the mixture of materials to be agglomerated passes onto a conveyor belt 7 and then into a sampler 8. The quantity 9 of the material which is not sampied, is taken directly to the head of the agglomerating con veyor 10, whilst the sampled quantity 11 drops from the sampler 8 onto a small conveyor belt 12 which deflects the materials 11 into a device 13, such as a permeameter for example, for measuring the permeability of the said materials.

At the output from the device 13, the materials illustrated by the arrow 14 are generally returned to the head of the agglomerating conveyor 10. After being roasted on the agglomerating conveyor belt 10, the thus sintered and agglomerated materials 15 are first of all screened in the hot properties of the agglomerated state through a screen 16, the major part of the material passing through the screen 16 and being'recycled (in accordance with arrows 17, 1 8, 19) through the fines hopper 2. The fraction of material held back by the screen 16 is evaluated as being of the desired quality and is dispatched (in accordance with the arrow 20 to the user, for example a blast furnace operator. A small fraction of the material passing through the screen 16 is deflected in accordance with the arrows 21 and 22 to a hot screen 23, and then to a high-speed cooling device 24. On leaving the latter device the said agglomerated materials are introduced into a device 25, for example a permagnag, for measuring the magnetic properties of said materials. After having passed the device 25, these materials are recycled in accordance with the arrows 26, 27, 18 and 19 via the tines hopper 2.

Although the measurement of the permeability of the materials to be agglomerated has been illustrated in the draw ing as taking place at'a location situated between the mill 5 and the agglomeration conveyor 10, it should be pointed out that this measurement can be taken at any desired location in the circuit through which the materials to be agglomerated pass, even upstream of the mill 5, for example at the exit from the hoppers l, 2 and 3.

On the basis of these considerations, the invention provides in a method of agglomerating mineral materials by mixing mineral materials, fuel, return fines and water and then sintering the resultant mixture: the improvement of continuously monitoring the process of agglomeration by measuring the permeability of the mixture before sintering and regulating the supply of water to ensure an appropriate permeability of the mixture to be sintered for the highest speed of sintering and for the desired quality of the agglomerate, said regulation of water supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process.

The process of agglomeration may be monitored by measuring the permeability (P) of the mixture before sintering and regulating the supply (0) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speed of sintering process and to the desired quality of the agglomerate, said regulation of water supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and regulating the supply (Q) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed positive value of the ratio (AP/A0) which essentially corresponds, at each moment, to the highest speed of sintering and to the desired quality of the agglomerate, (AP) and (A0) representing coordinate variations of the permeability (P) of the mixture beforesintering and of the quantity (0) of water supplied to said mixture, said regulation of water supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the magnetic properties of said agglomerated material as an indication of the quality of the agglomerate and regulating the supply of fuel to ensure appropriate magnetic properties of said agglomerated material after sintering for the desired quality of the agglomerate and for the lowest consumption of fuel, said regulation of fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring a magnetic index (Ml) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and regulating the supply of fuel (C) to ensure appropriate magnetic properties of said agglomerated material after sintering by means of an adjustable fixed value (Mlc) of said magnetic index which essentially corresponds, at each moment, to the desired quality of the agglomerate and to the lowest possible consumption of fuel, said regulation of fuel supply being made so as to take account of the dynamics of the process as a whole and" of foreseeable disturbances in the process.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and regulating the supply (Q) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speed of sintering process and to the desired quality of the agglomerate, said fixed value (Pc) of the permeability (P) being determined by means of an adjustable fixed positive value of the ratio (AP/A0) which essentially corresponds at each moment, to the highest speed of sintering and to the desired quality of the agglomerate, (AP) and (A0) representing coordinate variations of the permeability (P) of the mixture before sintering and of the quantity (0) of water supplied to said mixture, said regulation of water supply being made so as to take account of. the dynamics of the process as a whole and of foreseeable disturbances in the process.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and regulating the supply (Q) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speed of sintering process and to the desired quality of the agglomerate, and by measuring a magnetic index (Ml) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and regulating the supply of fuel (C) to ensure appropriate magnetic properties of said agglomerated material after sintering by means of an adjustable fixed value (Mlc)of said magnetic index which essentially corresponds, at each moment, to the desired quality of the agglomerate and to the lowest possible consumption of fuel, said regulations of water and fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process, and of the effect of changes in the moisture content of the mixture on the magnetic properties.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and regulating the supply (Q) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed positive value of the ratio (AP/A0) which essentially corresponds, at each moment, to the highest speed of sintering and to the desired quality of the agglomerate, (AP) and (A0) representing coordinate variations of the permeability (P) of the mixture before sintering and of the quantity (0) of water supplied to said mixture, and by measuring amagnetic index (Ml) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and regulating the supply of fuel (C) to ensure appropriate magnetic properties of said agglomerated material after sintering by means of an adjustable fixed value (Mic) of said magnetic index which essentially corresponds, at each moment, to the desired quality of the agglomerate and to the lowest possible consumption of fuel, said regulations of water and fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process and of the effect of changes in the moisture content of the mixture on the magnetic properties of the agglomerate.

The invention further consists in the improvement of continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and by regulating the supply (Q) of water to ensure an appropriate permeability of the mixture to be sintered by means of an adjustable fixed value (Pc) of the permeability (1?), said value essentially corresponding, at each moment, to the highest speed of the sintering process and to the desired quality of the agglomerate, said fixed value of the permeability )P) of the mixture before sintering being adjusted. by means of an adjustable fixed positive value of the ratio (AP/AQ) which essentially corresponds, at each moment, to the highest speed of sintering and to the desired quality of the agglomerate, (AP) and (AQ) representing coordinate variations of the permeability (P) of the mixture before sintering of the quantity (Q) of water supplied to said mixture; and by measuring a magnetic index (Ml) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and regulating the supply of fuel (C) to ensure appropriate magnetic properties of said agglomerated material after sintering by means of an adjustable fixed value (Mile) of said magnetic index which essentially corresponds at each moment, to the desired quality of the agglomerate and to the lowest possible consumption of fuel, said regulations of water and fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process and of the effect of changes in the moisture content of the mixture on the magnetic properties of the agglomerate.

In the case where the main feed hopper of the agglomerating system proper, is equipped with a roller feed system, measurement of the permeability will be carried out directly in said main hopper.

In the case where the agglomeration system proper is fed by an oscillating chute and vibratory feed system, measurement of the permeability will be carried out in a small auxiliary hopper into which there is branched off, using some appropriate means, part of the material which is to be agglomerated.

If the measure value of the permeability is other than the setpoint value, the addition of water is reduced or increased in accordance with whether the said error is positive or negative, this until said error is cancelled out, while checking to ensure that a reduction in the water input does correspond to a reduction in the permeability, and vice versa.

In accordance with one advantageous mode of operation of the invention, the device for adding water to the materials to be agglomerated is linked to the permeability-measuring apparatus, which obviates any necessity for external intervention in the regulating system.

In accordance with the invention, the sample continuously picked up at the output of the agglomerating system proper, is advantageously composed solely of return fines.

Experience has shown that there is an excellent correlation between the characteristics of the agglomerates and those of the fines. The continuous measurement of the magnetic properties of the fines has the advantage that it avoids any need for crushing the materials.

With the object of supplying the apparatus for measuring the magnetic properties, with materials of suitable and constant grain size, despite wear in the screen used at the output of the agglomerating system proper, the sampled return fines will advantageously be screened a second time prior to cooling and introduction into the measuring apparatus.

in accordance with an advantageous mode of operation of the invention, the devices responsible for determining the input variables of the agglomerating apparatus, such as for example the device for adding the fuel, are linked to the apparatus for measuring the magnetic permeability, and this obviates any necessity for external intervention in the regulating system.

in accordance with another mode of operation of the invention, at least the setpoint values of the permeability of the agglomerated materials, are determined, a sample of the materials to be agglomerated is taken at a point situated upstream of the agglomerating conveyor belt, between said belt and the device which adds the water, this sample is processed through an auxiliary agglomerating apparatus where successive and appropriate operations of roasting and cooling are carried out, subsequently the cooled material is treated either by screening or by crushing, then a predetermined fraction of the materials thus treated is introduced into an apparatus for measuring the magnetic properties, and, finally, as a function of the values obtained, the input variables of the agglomeration conveyor belt are regulated in order to control out the error between the setpoint values and the measured values within the shortest possible time.

In accordance with the invention, the auxiliary agglomerating apparatus will advantageously take the form of a conveyor belt device and the material will be distributed upon this device in a layer having a substantially smaller thickness than the layer of material carried on the main belt.

In order to standardize the measurement of the magnetic properties of the agglomerated materials, the processing through the auxiliary conveyor belt agglomerating device, is carried out under conditions of constant ignition, constant vacuum and desired permeability.

It is advantageous in accordance with the invention to exploit the sampling carried out in order to measure the permeability of the materials which are to be agglomerated, in order to use said sample, at exit from the permeability-measuring device, for agglomeration processing, and ultimately in order to introduce said agglomerated materials into a device for measuring the magnetic properties.

FIG. 2 illustrates in block form the control loops for the water and fuel supplies and also an optimalization loop for the water supply.

The control loop for the water supply includes a valve 31 for adjusting the quantity (Q) of water supplied to the mixture to be sintered, a control block 32 representing the operation of mixing mineral materials, a control block 33 representing the operation of preparation of a sample representative of the mixture before sintering and of measurement of the permeability (P) of said sample, a block 34 of comparing the actual measured value of said permeability (P) with the fixed value (Pc) of said permeability, said fixed value (Pc) being displayed in a device 35 such as a potentiometer, a control block 36 taking account of the possible difference between the actual measured value (P) and the fixed value (Fe) in order to actuate the valve 31 in order to change the quantity of water supplied so as to eliminate said difference in the shortest time.

It is to be noted that the blocks 32 and 36 are designed in order to take account of the dynamics of the process and of foreseeable disturbances of the process involved in the regulation loop for the water supply.

The optimization loop for the water supply includes the valve 31, the control blocks 32, 33, 34, and 36 of the control loop of water supply, and in addition:

a. a device (not illustrated) for measuring the moisture content of the mineral materials entering in the constitution of the mixture to be sintered;

b. a control block 37 which receives the indications:

on one hand, of the above-mentioned moisture content of the mineral materials to be sintered on the other hand, of the actual value of the permeability (P) of said mixture, from the control block, 33 and which delivers a signal representative of the real value ratio (AP/AQ) and which compares said signal of the real value of the ratio (AP/A) with a signal representative of a fixed value (AP/AQ) c of said ratio;

c. a control block 39 for taking account of the possible difference between the actual value (AP/AQ) and the fixed value (AP/AQ)c in order to: either directly actuate the value 31 in order to change the quantity of water supplied so as to cancel said difference in the shortest time or to send to the block 34 a signal representative of a fixed value of the permeability (P) of the mixture to be sintered, said fixed value (P) being compared by means of the regulation block 34 with the actual measured value of permeability (P) coming from the regulation block 33, and then if there is a difference between said values, the regulation block 36 enters into action in order to actuate the valve 31 in order to change the quantity of water supplied so as to cancel said difference in the shortest time.

It is to be noted in said second alternative that the link between the device 35 and the block 34 is interrupted so as to get an automatic fixed value (P), of the permeability based on the value of the fixed value of the ratio (AP C/AQ).

The regulation loop for the fuel supply includes:

a valve 40 for adjusting the quantity (C) of fuel supplied to the mixture to be sintered, 41 a control block 4 representing the operation of sintering (strand, and ancillaries other than mixers of the mineral materials to be sintered), a control block 42 representing the operation of preparation of a sample representative of the agglomerated materials and of measurement of the magnetic index (MI) of said sample, said index being in relation with the magnetic properties of said agglomerated materials, said magnetic properties being representative of the quality of the agglomerate, a control block 43 of comparing the real measured value of said magnetic index (MI) with the fixed value (Ml)c of said magnetic index, said fixed value (IM)c being displayed in a device 44,

. such as a potentiometer, a control block 45 for taking account of the possible difference between the real measured value (MI) and the fixed value (Ml)c in order to actuate the fuel valve 40 in order to change the quantity of fuel supplied so as to cancel said difference in the shortest time.

It is to be noted that the arrow 46 indicates foreseeable perturbations of which account is to be taken in the regulation of the sintering process. In the same way, the arrow 47 indicates factors which can produce some disturbances in the mixing process represented by the block 32 and consequently in the sintering process.

Interaction between the control loops for the water supply and for the fuel supply is represented by the link 48-49 which involves both the block 32 representing the mixing process and the block 41 representing the sintering process.

We claim:

1. In a method of agglomerating mineral materials by mixing mineral materials having magnetic properties, fuel, return fines and water and then sintering the resultant mixture: the improvement comprising continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and automatically regulating the supply (Q) of water in response to said measuring to ensure an optimum permeability of the mixture to be sintered by comparing to an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speed of sintering process consistent with the desired quality of the agglomerate; then measuring a magnetic index (MI) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerateand automatically regulating the supply of fuel (C) in response to said magnetic index measuring to ensure optimum magnetic properties of said agglomerated material after sintering by comparing to an adjustable fixed value (MIc) of said magnetic index which value essentially corresponds, at each moment, to the desired quality of the agglomerate consistent with the lowest possible consumption of fuel; selection of each of said adjustable fixed values, and said regulations of water and fuel supply taking into account the dynamics of the process as a whole and the foreseeable disturbances in the process; continuing to control the process of agglomeration by simultaneously measuring said permeability and magnetic properties in response to the adjustable fixed values (Pc,MIc) respectively and regulating the supply of water and fuel as aforesaid.

2. A method as claimed in claim 1 in which said measuring of the magnetic index (MI) is carried out on samples continuously taken at the output of the sintered agglomerate, said samples being composed solely of return fines.

3. The method as claimed in claim 2 wherein said samples continuously taken at the output of the sintered agglomerate must be of substantially constant grain size and comprising the additional steps of screening said return fines and then cooling the screened fines before measuring the magnetic index.

4. In a method of agglomerating mineral materials by mixing mineral materials having magnetic properties, fuel, return fines and water and then sintering the resultant mixture; the improvement comprising continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and by automatically regulating the supply (Q) of water in response to said measuring to ensure an optimum permeability of the mixture to be sintered by comparing to an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speed of the sintering process consistent with the desired quality of the agglomerate, said fixed value of the ratio AP/AQ which essentially corresponds, at each moment, to the highest speed of sintering consistent with the desired quality of the agglomerate, (AP) and (A) representing coordinate variations of the permeability (P) of the mixture before sintering of the quantity (Q) of water supplied to said mixture; then measuring a magnetic index (Ml) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and automatically regulating the supply of fuel (C) in response to said measuring to ensure optimum magnetic properties of said agglomerated material after sintering by comparing to an adjustable fixed value (Mlc) of said magnetic index which essentially corresponds, at each moment, to the desired quality of the ag glomerate and to the lowest possible consumption of fuel; selection of each of said adjustable fixed values, and said regulations of water and fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process; continuing to control the process of agglomeration by simultaneously measuring said permeability and magnetic properties in response to the adjustable fixed values (Pc, Mlc) respectively and regulating the supply of water and fuel as aforesaid.

5. A method as claimed in claim ll in which said measuring of the magnetic index (MI) is carried out on samples continuously taken at the output of the sintered agglomerate, said samples being composed solely of return fines.

6. The method as claimed in claim 5 wherein said samples continuously taken at the output of the sintered agglomerate must be of substantially constant grain size and comprising the additional steps of screening said return fines and then cooling the screened fines before measuring the magnetic index. 

2. A method as claimed in claim 1 in which said measuring of the magnetic index (MI) is carried out on samples continuously taken at the output of the sintered agglomerate, said samples being composed solely of return fines.
 3. The method as claimed in claim 2 wherein said samples continuously taken at the output of the sintered agglomerate must be of substantially constant grain size and comprising the additional steps of screening said return fines and then cooling the screened fines before measuring the magnetic index.
 4. In a method of agglomerating mineral materials by mixing mineral materials having magnetic properties, fuel, return fines and water and then sintering the resultant mixture; the improvement comprising continuously monitoring the process of agglomeration by measuring the permeability (P) of the mixture before sintering and by automatically regulating the supply (Q) of water in response to said measuring to ensure an optimum permeability of the mixture to be sintered by comparing to an adjustable fixed value (Pc) of the permeability (P), said value essentially corresponding, at each moment, to the highest speeD of the sintering process consistent with the desired quality of the agglomerate, said fixed value of the ratio Delta P/ Delta Q which essentially corresponds, at each moment, to the highest speed of sintering consistent with the desired quality of the agglomerate, ( Delta P) and ( Delta Q) representing coordinate variations of the permeability (P) of the mixture before sintering of the quantity (Q) of water supplied to said mixture; then measuring a magnetic index (MI) representing the magnetic properties of the agglomerated material after sintering as an indication of the quality of the agglomerate and automatically regulating the supply of fuel (C) in response to said measuring to ensure optimum magnetic properties of said agglomerated material after sintering by comparing to an adjustable fixed value (MIc) of said magnetic index which essentially corresponds, at each moment, to the desired quality of the agglomerate and to the lowest possible consumption of fuel; selection of each of said adjustable fixed values, and said regulations of water and fuel supply being made so as to take account of the dynamics of the process as a whole and of foreseeable disturbances in the process; continuing to control the process of agglomeration by simultaneously measuring said permeability and magnetic properties in response to the adjustable fixed values (Pc, MIc) respectively and regulating the supply of water and fuel as aforesaid.
 5. A method as claimed in claim 4 in which said measuring of the magnetic index (MI) is carried out on samples continuously taken at the output of the sintered agglomerate, said samples being composed solely of return fines.
 6. The method as claimed in claim 5 wherein said samples continuously taken at the output of the sintered agglomerate must be of substantially constant grain size and comprising the additional steps of screening said return fines and then cooling the screened fines before measuring the magnetic index. 